mcount.c

/*- * Copyright (c) 1983, 1992, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */#if !defined(lint) && !defined(KERNEL) && defined(LIBC_SCCS)staticchar sccsid[] = "@(#)mcount.c 8.1 (Berkeley) 6/4/93";
#endif#include <unistd.h>#include <sys/param.h>#include <sys/gmon.h>/* This file provides the machine-dependent definitions of the _MCOUNT_DECL and MCOUNT macros. */#include <machine-gmon.h>#include <atomic.h>/* * mcount is called on entry to each function compiled with the profiling * switch set. _mcount(), which is declared in a machine-dependent way * with _MCOUNT_DECL, does the actual work and is either inlined into a * C routine or called by an assembly stub. In any case, this magic is * taken care of by the MCOUNT definition in <machine/profile.h>. * * _mcount updates data structures that represent traversals of the * program's call graph edges. frompc and selfpc are the return * address and function address that represents the given call graph edge. * * Note: the original BSD code used the same variable (frompcindex) for * both frompcindex and frompc. Any reasonable, modern compiler will * perform this optimization. */
_MCOUNT_DECL(frompc, selfpc) /* _mcount; may be static, inline, etc */
{
register ARCINDEX *frompcindex;
registerstruct tostruct *top, *prevtop;
registerstruct gmonparam *p;
register ARCINDEX toindex;
int i;
p = &_gmonparam;
/* * check that we are profiling * and that we aren't recursively invoked. */if (catomic_compare_and_exchange_bool_acq (&p->state, GMON_PROF_BUSY,
GMON_PROF_ON))
return;
/* * check that frompcindex is a reasonable pc value. * for example: signal catchers get called from the stack, * not from text space. too bad. */
frompc -= p->lowpc;
if (frompc > p->textsize)
goto done;
/* The following test used to be if (p->log_hashfraction >= 0) But we can simplify this if we assume the profiling data is always initialized by the functions in gmon.c. But then it is possible to avoid a runtime check and use the smae `if' as in gmon.c. So keep these tests in sync. */if ((HASHFRACTION & (HASHFRACTION - 1)) == 0) {
/* avoid integer divide if possible: */
i = frompc >> p->log_hashfraction;
} else {
i = frompc / (p->hashfraction * sizeof(*p->froms));
}
frompcindex = &p->froms[i];
toindex = *frompcindex;
if (toindex == 0) {
/* * first time traversing this arc */
toindex = ++p->tos[0].link;
if (toindex >= p->tolimit)
/* halt further profiling */goto overflow;
*frompcindex = toindex;
top = &p->tos[toindex];
top->selfpc = selfpc;
top->count = 1;
top->link = 0;
goto done;
}
top = &p->tos[toindex];
if (top->selfpc == selfpc) {
/* * arc at front of chain; usual case. */
top->count++;
goto done;
}
/* * have to go looking down chain for it. * top points to what we are looking at, * prevtop points to previous top. * we know it is not at the head of the chain. */for (; /* goto done */; ) {
if (top->link == 0) {
/* * top is end of the chain and none of the chain * had top->selfpc == selfpc. * so we allocate a new tostruct * and link it to the head of the chain. */
toindex = ++p->tos[0].link;
if (toindex >= p->tolimit)
goto overflow;
top = &p->tos[toindex];
top->selfpc = selfpc;
top->count = 1;
top->link = *frompcindex;
*frompcindex = toindex;
goto done;
}
/* * otherwise, check the next arc on the chain. */
prevtop = top;
top = &p->tos[top->link];
if (top->selfpc == selfpc) {
/* * there it is. * increment its count * move it to the head of the chain. */
top->count++;
toindex = prevtop->link;
prevtop->link = top->link;
top->link = *frompcindex;
*frompcindex = toindex;
goto done;
}
}
done:
p->state = GMON_PROF_ON;
return;
overflow:
p->state = GMON_PROF_ERROR;
return;
}
/* * Actual definition of mcount function. Defined in <machine/profile.h>, * which is included by <sys/gmon.h>. */
MCOUNT